1. Field of the Invention
The present invention relates to a novel automotive headlamp. More particularly, the invention relates to an automotive headlamp having a gear apparatus for an aiming mechanism or the like, in which gear apparatus a gear shaft hardly rotates with respect to a gear shaft supporting wall while the gear shaft is in a non-rotation state, whereas, in contrast, the gear shaft is allowed to rotate smoothly while the gear shaft is in a rotation state.
2. Related Art
A conventional automotive headlamp having the gear apparatus is, for example, employed as a part of an aiming mechanism in which a tip end portion of an aiming screw unrotatably engages with a headlamp unit through a receiving member, and a first gear threadably mounted on a threaded shaft part of the aiming screw engages with a second gear linked to an operation shaft.
When the second gear is rotated by operating the operation shaft, the first gear engaging with the second gear starts to rotate. Since the aiming screw is unrotatable the threaded shaft part of which is urged to move back or forth so that the aiming screw moves in an axial direction thereof. Therefore, a position of a portion of the headlamp unit where the receiving member is supported varies to tilt the headlamp unit.
In the conventional mechanism, a load is applied against a rotational force of the gear in order to prevent the gear from rotating during non-operation condition of the operation shaft due to an external vibration such as a vibration generated while the automobile is travelling.
According to an automotive headlamp having the conventional gear apparatus as described above, since a load is applied against a rotational force of the gear, a relatively strong operational force is required for operating the operation shaft. Therefore, it may be difficult to operate the gear is not. On the other hand, if the load applied against the rotational force of the gear is lowered to make it easier to operate the gear, the gear may be readily rotated due to an external vibration applied to the gear.